This invention relates to a supporting member or spring material that requires good electrical conductivity and high mechanical strength. Conventional structural members are usually made of high strength iron or steel material and in applications that require corrosion resistance, stainless steels are generally used. Those components of electrical machines which require good electrical conductivity are made of copper-based materials. Phosphor bronze is selected for certain spring materials that require high electrical conductivity and beryllium-copper and titanium-copper alloys are used if a higher mechanical strength is required. However, the mechanical strength of phosphor bronze is low whereas beryllium-copper and titanium-copper alloys are very expensive and have low rigidity. Therefore, these copper alloys do not provide springs that perform as well as those made of steel-based materials. The tensile strength vs conductivity profile of six conventional copper alloys is shown in FIG. 1. As shown in FIG. 1 (A) is Cu-Ni, (B) is Cu-Ti, (C) is Be-Cu, (D) is Cu-Fe, (E) is Cu-Cd and (F) is pure copper.
The primary object of the present invention is to provide a material having both good electrical conductivity and high mechanical strength, identified by region G in FIG. 1. In this region superior results are attained.
Another object of the invention is to provide an inexpensive spring material and a highly conductive supporting member.
These and other objects of this invention are accomplished by an electrically conductive composite material having a copper core and an iron-or nickel-base alloy clad material. The cross-sectional ratio of the clad material to the core is 0.1.ltoreq.Se/Se+Scu.ltoreq.0.8 where Se is the cross-sectional area of the clad material and Scu is the cross-sectional area of the copper core. Additionally, the tensile strength P in kg/mm.sup.2 is: 230-1.9 (100Scu+2.3Se)/(Se+Scu).gtoreq.P.gtoreq.80-0.4 (100Scu+2.3Se)/(Se+Scu). The clad material may be iron, steel, alloyed steel, stainless steel or a steel inner layer and a stainless steel outer layer. This invention will be defined in greater detail by reference to the drawings and the description of the preferred embodiment that follows.